For many people the more interesting thing is webOS 2.0 and if it will run on the early webOS-devices. Until now there is no clear statement from HP about that question. But in The Official Palm Blog you can read:

Here’s a quick rundown on what you can expect when the update becomes available for your phone:

As the PRE 2 will run on webOS 2.0 from the beginning this could only mean that it will also run on the old phones too.